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Abstract:

A method of treating untreated low calorific coal containing moisture and
organic volatiles includes feeding untreated coal to a dryer, and drying
the coal. The dried coal is subjected to a pyrolyzing step where
oxygen-deficient gases are brought into contact with the coal, thereby
lowering the volatile content of the coal and producing a stream of
pyrolysis effluent gases. The pyrolysis effluent gases are subjected to a
separation process to separate lean fuel gases from liquids and tars,
wherein the separation process removes less than about 20 percent of the
pyrolysis effluent gases as the liquids and tars, with the remainder
being the lean fuel gases. The lean fuel gases are returned to the dryer
combustor, the pyrolyzer combustor, or the pyrolyzer.

Claims:

1. A method of treating untreated low calorific coal containing moisture
and organic volatiles, the method comprising: operating a dryer combustor
for producing gases for drying coal; feeding untreated coal to a dryer,
and drying the coal; operating a pyrolyzer combustor for producing gases
for pyrolyzing; subjecting the dried coal to a pyrolyzing step in a
pyrolyzer where oxygen-deficient gases are brought into contact with the
coal, thereby lowering the volatile content of the coal and producing a
stream of pyrolysis effluent gases; subjecting the pyrolysis effluent
gases to a separation process to separate lean fuel gases from liquids
and tars, wherein the separation process removes less than about 20
percent of the pyrolysis effluent gases as the liquids and tars, with the
remainder being the lean fuel gases; and returning the lean fuel gases to
one or more of the dryer combustor, the pyrolyzer combustor, or the
pyrolyzer.

2. The method of claim 1 in which the separation process removes less
than about 10 percent of the pyrolysis effluent gases as the liquids and
tars.

3. The method of claim 1 in which the untreated coal has a fuel ratio
less than about 0.60.

4. The method of claim 1 in which the atomic hydrogen to carbon (H/C)
ratio less than about 0.65.

5. The method of claim 1 in which the untreated coal has less than about
35 percent volatile content.

6. The method of claim 1 in which the pyrolyzing process is carried out
in a manner resulting in production of char having volatile matter in an
amount within the range of from about 10 to about 20 percent.

7. The method of claim 1 in which the pyrolyzing process is carried out
in a manner in which at least 20 percent of the at least 25 percent of
the volatiles from the coal are driven off in the pyrolysis process.

8. The method of claim 1 in which the treating of untreated low calorific
coal is effective to raise the thermal value of low calorific coal having
a calorific content of less than or equal to about 8,000 Btu/pound (18.6
MJ/kg) to a resulting stream of processed coal having a thermal value of
at least about 11,000 Btu/pound (25.6 MJ/kg).

9. The method of claim 1 in which the resulting processed coal char has
its sulfur content reduced by over 35 percent when compared with the
untreated coal.

10. A method of treating untreated low calorific coal containing moisture
and organic volatiles, the method comprising: operating a dryer combustor
for producing gases for drying coal; feeding untreated coal to a dryer,
and drying the coal; operating a pyrolyzer combustor for producing gases
for pyrolyzing; subjecting the dried coal to a pyrolyzing step in a
pyrolyzer where oxygen-deficient gases are brought into contact with the
coal, thereby lowering the volatile content of the coal and producing a
stream of pyrolysis effluent gases; subjecting the pyrolysis effluent
gases to a separation process to separate lean fuel gases from liquids
and tars, wherein the separation process is carried out while maintaining
the pyrolysis effluent gases at a temperature above the condensation
temperature of the pyrolysis effluent gases; and returning the lean fuel
gases to one or more of the dryer combustor, the pyrolyzer combustor, or
the pyrolyzer.

11. The method of claim 10 in which the separation process removes less
than about 10 percent of the pyrolysis effluent gases as the liquids and
tars.

12. The method of claim 10 in which the untreated coal has a fuel ratio
less than about 0.60.

13. The method of claim 10 in which the atomic hydrogen to carbon (H/C)
ratio less than about 0.65.

14. The method of claim 10 in which the untreated coal has less than
about 35 percent volatile content.

15. The method of claim 10 in which the pyrolyzing process is carried out
in a manner resulting in production of char having volatile matter in an
amount within the range of from about 10 to about 20 percent.

16. The method of claim 10 in which the treating of untreated low
calorific coal is effective to raise the thermal value of low calorific
coal having a calorific content of less than or equal to about 8,000
Btu/pound (18.6 MJ/kg) to a resulting stream of processed coal having a
thermal value of at least about 11,000 Btu/pound (25.6 MJ/kg).

17. A method of treating untreated low calorific coal containing moisture
and organic volatiles, the method comprising: operating a dryer combustor
for producing gases for drying coal; feeding untreated coal to a dryer,
and drying the coal; operating a pyrolyzer combustor for producing gases
for pyrolyzing; subjecting the dried coal to a pyrolyzing step in a
pyrolyzer where oxygen-deficient gases are brought into contact with the
coal, thereby lowering the volatile content of the coal and producing a
stream of pyrolysis effluent gases; subjecting the pyrolysis effluent
gases to a separation process to separate lean fuel gases from liquids
and tars, wherein the separation process is carried out without
substantial cooling of the pyrolysis effluent gases; and returning the
lean fuel gases to one or more of the dryer combustor, the pyrolyzer
combustor, or the pyrolyzer.

18. The method of claim 17 in which the untreated coal has a fuel ratio
less than about 0.60, the atomic hydrogen to carbon (H/C) ratio less than
about 0.65, and the untreated coal has less than about 35 percent
volatile content.

19. The method of claim 17 in which the pyrolyzing process is carried out
in a manner resulting in production of char having volatile matter in an
amount within the range of from about 10 to about 20 percent.

20. The method of claim 17 in which the treating of untreated low
calorific coal is effective to raise the thermal value of low calorific
coal having a calorific content of less than or equal to about 8,000
Btu/pound (18.6 MJ/kg) to a resulting stream of processed coal having a
thermal value of at least about 11,000 Btu/pound (25.6 MJ/kg).

Description:

RELATED APPLICATIONS

[0001] None.

TECHNICAL FIELD

[0002] This invention relates to a method of processing coal, such as
noncaking, noncoking coal, to form coal char in an upgraded form. More
particularly, this invention relates to a process for treating low rank
coal having low condensable oil content.

BACKGROUND OF THE INVENTION

[0003] A principal objective of coal benefication is to increase the
calorific heating value or amount of thermal energy of the coal that can
be released during a subsequent combustion process. One method of
increasing the thermal energy released during combustion of coal is to
decrease the amount of moisture by subjecting the coal to a drying
process. It will be appreciated that moisture in coal has no heating
value and, although not environmentally harmful, facilitates depletion
because evaporation of the moisture consumes a portion of thermal energy
released during combustion of coal.

[0004] Another known method of increasing the thermal energy released
during combustion of coal is to decrease the amount of volatile matter
within the coal, and thereby increase the relative amount of fixed carbon
in the coal. The amount of volatile matter within coal may be decreased
by subjecting the coal to a pyrolysis process. Pyrolysis of coal in an
oxygen deficient atmosphere removes volatile matter, e.g. low boiling
point organic compounds and some heavier organic compounds, by breaking
chemical bonds during the heating process. Breaking chemical bonds within
coal during the heating process increases the relative percentage of
elemental carbon which provides most of the calorific heating value when
coal is burned.

[0005] A by-product of the pyrolysis step is a stream of volatile gases.
There are known methods for processing the volatile materials released
from the pyrolysis step, to condense the volatile materials into liquids
for fuel and other associated products. However, where the raw coal
contains little oil in its initial state, producing significant amounts
of oil and other associated products will be difficult. Therefore, it
would be advantageous if there could be developed an improved coal
upgrading process for low rank coal having an initial low oil content.

SUMMARY OF THE INVENTION

[0006] According to this invention there is provided a method for treating
is untreated low calorific coal containing moisture and organic
volatiles. The method includes feeding untreated coal to a dryer, and
drying the coal. The dried coal is subjected to a pyrolyzing step where
oxygen-deficient gases are brought into contact with the coal, thereby
lowering the volatile content of the coal and producing a stream of
pyrolysis effluent gases. The pyrolysis effluent gases are subjected to a
separation process to separate lean fuel gases from liquids and tars,
wherein the separation process removes less than about 20 percent of the
pyrolysis effluent gases as the liquids and tars, with the remainder
being the lean fuel gases. The lean fuel gases are returned to the dryer
combustor, the pyrolyzer combustor, or the pyrolyzer.

[0007] According to this invention there is also provided a method of
treating untreated low calorific coal containing moisture and organic
volatiles. The method includes feeding untreated coal to a dryer, and
drying the coal. The dried coal is subjected to a pyrolyzing step where
oxygen-deficient gases are brought into contact with the coal, thereby
lowering the volatile content of the coal and producing a stream of
pyrolysis effluent gases. The pyrolysis effluent gases are subjected to a
separation process to separate lean fuel gases from liquids and tars,
wherein the separation process is carried out while maintaining the
pyrolysis effluent gases at a temperature above the condensation
temperature of the pyrolysis effluent gases. The fuel gases are returned
to the dryer combustor, the pyrolyzer combustor, or the pyrolyzer.

[0008] According to this invention there is also provided a method of
treating untreated low calorific coal containing moisture and organic
volatiles. The method includes feeding untreated coal to a dryer, and
drying the coal. The dried coal is subjected to a pyrolyzing step where
oxygen-deficient gases are brought into contact with the coal, thereby
lowering the volatile content of the coal and producing a stream of
pyrolysis effluent gases. The pyrolysis effluent gases are subjected to a
separation is process to separate lean fuel gases from liquids and tars,
wherein the separation process is carried out without substantial cooling
of the pyrolysis effluent gases. The fuel gases are returned to the dryer
combustor, the pyrolyzer combustor, or the pyrolyzer.

[0009] Various advantages of this invention will become apparent to those
skilled in the art from the following detailed description of the
preferred embodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

[0010] FIG. 1 is a schematic view of a coal upgrading process.

DETAILED DESCRIPTION OF THE INVENTION

[0011] This invention is directed to treating low calorific or low rank
coal. In one example, low calorific coal has about 30 percent moisture,
about 20 percent organic volatile content, and about 5 percent ash, with
the remainder being fixed carbon. All expressions of percentages of
constituents are expressed in terms of weight percent. In this example,
the low calorific coal has a thermal content of less than or equal to
about 8,000 Btu/pound (18.6 MJ/kg), although the Btu content can be
higher or lower. Coal of such a low heat content is insufficient for many
potential uses for coal, and it is desirable to treat the low calorific
coal to produce coal of higher thermal content. Further, in situations
where the coal must be transported long distances to reach the ultimate
destination of use, it is beneficial to treat the low rank coal prior to
transporting the coal.

[0012] As shown in FIG. 1, the apparatus for treating low calorific coal
is indicated at 10. A supply of low calorific value raw coal is indicated
at 12. Optionally the low calorific coal is processed in a sizing
apparatus, such as a coal crusher, not shown, for is sizing the untreated
raw coal to a size desired for the additional steps of the process.
Crushers and other apparatus for sizing the coal, not shown, can be used
to assure that the maximum coal particle size of the crushed coal doesn't
exceed a selected value for additional process steps. Apparatus for
crushing and sizing are well known in the art.

[0013] The coal is introduced into the coal dryer 14 where the coal is
heated with hot dryer gases 16 to remove moisture from the coal. Effluent
from the coal drying process is indicated at 18. The coal dryer 14 is a
rotary dryer in which the coal traverses a spiral path from the outer
circumference to the center. The dryer 14 has bottom hot gas inlet vents
that allow hot dryer gases to pass into contact with the coal for drying.
Other dryers can also be used. The residence time for the coal in the
dryer, the hot gas flow path, and the temperature of the hot dryer gases
are all controlled to provide the appropriate amount and quality of
heating of the coal. Any suitable dryer apparatus can be used for the
coal drying step. Untreated raw low rank coal typically has an
equilibrium moisture level within the range of from about 15 to about 35
percent, although it can be higher or lower. Therefore, the low rank coal
12 introduced into the dryer 14 will typically have a moisture content
within that range. In the drying process, the moisture content is
typically reduced to a level below about 10 percent, and in some
embodiments to a level within the range of from about 3 to about 5
percent.

[0014] It is desirable to maintain the dryer hot gases 16 at a temperature
low enough to preclude or prevent any significant amounts of
volatilization of volatile components of coal, such as, for example,
carbon monoxide and hydrocarbons. When volatilization is prevented, the
dryer effluent 18 does not require a significant burn off process that
would otherwise be necessary to prevent the discharge of undesirable
gases. The temperature of the dryer gases 16 is typically kept at a level
below about 600° F. In one embodiment, the temperature is kept
below about 500° F. After the coal is dried, it is exits the dryer
14 as a stream of dried coal 20.

[0015] As further shown in FIG. 1, the dried coal 20 is introduced into a
pyrolyzer 22. The pyrolyzer 22 is a rotary pyrolyzer, and is a closed
container to control the flow of material and gases into and out of the
container. Hot gases for pyrolysis, indicated at 24, are introduced into
the pyrolyzer and brought into contact with the dried coal 20. The gases
that evolve or are released from the pyrolyzer 22 are the pyrolysis
effluent gases 26.

[0016] The pyrolyzer 22 can be any apparatus suitable for interacting the
pyrolyzing gases with the coal. For example, the pyrolyzer can be a
fluidized bed apparatus. A rotary pyrolyzer can also be used. The hot
pyrolyzing gases 24 are introduced at a temperature that causes the
pyrolyzing process to be operated as a mild pyrolyzing process. The hot
pyrolyzing gases 24 are oxygen deficient, typically having less than
about 0.5 percent free oxygen, and usually having no detectable free
oxygen. The temperature of the pyrolyzing gases is less than about
1100° F., and typically within the range of from about 700°
F. to about 900° F. In one embodiment, the pyrolyzing gases 24 are
within the range of from about 750° F. to about 850° F. In
a specific embodiment the pyrolyzer gases are introduced at a temperature
of about 800° F.

[0017] In the mild pyrolysis step of the process, a controlled amount of
hydrogen, oxygen and carbon in the forms of H2, CH4, CO2, CO, and H2O are
stripped from the coal. Other compounds such as coal tar liquids that are
volatile at these temperatures are also removed from the coal. The
pyrolysis conditions of temperature, gas flow rate, and residence time in
the pyrolyzer 22 are closely controlled so that only a limited amount of
pyrolysis effluent gases 26 is produced and the resulting processed coal
30 contains 10 to 20 percent volatile matter which is desirable for its
use as a boiler fuel. People skilled in the art will understand that the
pyrolysis effluent gas has value as a low heating value fuel. The
pyrolysis process is controlled to substantially produce only the amount
of pyrolysis gas sufficient to support the energy requirements of
subsequent heating steps. These subsequent heating steps are the heating
of the coal drying gases 16, the pyrolyzing gases 24, and the pyrolyzer
combustor 28. The mild pyrolysis of the pyrolyzer 22 produces this
limited amount of pyrolysis effluent gases while avoiding the production
of significant amounts liquid fuel products.

[0018] The upgrade of the coal in the pyrolyzer 22 produces a stream of
upgraded coal char, shown at 30. The coal char has been chemically
transformed so that it has a lower equilibrium moisture level than the
equilibrium moisture level of the raw coal 12. Typically the equilibrium
moisture level is reduced in the drying and pyrolysis process to a level
of less than about 10 percent, and in one embodiment to a level within
the range of from about 5 percent to about 10 percent. Also, the coal
char 30 leaving the pyrolyzer 22 has a significant portion of the lighter
volatiles removed. The thermal value of the char 30 has been upgraded to
a Btu value greater than about 10,000 Btu/lb (23.2 MJ/kg), in contrast to
the typical thermal level of about 8,000 Btu (18.6 MJ/kg) for the
incoming raw coal 12.

[0019] After leaving the pyrolysis step, the char 30 is quenched to
quickly lower the char temperature and stop the pyrolysis reaction. The
quenching step is carried out in a quench table 32, which can be any
suitable apparatus for applying a stream 34 of quenching water or other
quenching liquids. In one embodiment the quenching table 32 is a rotary
device. The quenching liquid can be any suitable liquid, typically water,
supplied from a source, not shown. Steam is produced in the quenching
table, and the exiting steam is indicated at 36. It is to be understood
that any suitable method and apparatus can be used to quench the treated
coal.

[0020] The quenched char 38 is then sent to additional plant equipment for
cooling and stabilization to reduce the tendency of the char to
spontaneously ignite. The type and amount of processing in these
additional steps is dependent on the final use of the char product. As
shown in FIG. 1, the quenched char 38 can optionally be subjected to a
rotary cooler 40 or other similar apparatus for additional cooling, and a
finishing reactor 42 where the char 38 is subjected to humidification and
stabilizing steps to assure that the resultant finished coal char 44 is
ready and stable for shipping and ultimately a combustion process.
Optionally, the cooling and finishing steps can be combined in a single
apparatus. Unlike the coal formed from a mere thermal drying of the coal,
this char product 44 has been upgraded from the initially supplied feed
coal 12. The upgraded char 44 has a significant reduction in total
moisture as well as a lower equilibrium moisture in comparison with the
moisture properties of the feed coal 12. It will be understood by people
skilled in the art that mere thermal drying of the coal does not reduce
the equilibrium moisture of the coal. They will also understand that coal
dried to a value below its equilibrium moisture will rehydrate to its
equilibrium moisture by contact with atmospheric air. Further, the
upgraded char product 30 has its burning characteristics significantly
enhanced, and some undesirable components such as sulfur have been
reduced. In a specific embodiment the resulting processed coal char had
its sulfur content reduced by over 35 percent in comparison with the
untreated coal. This reduction along with an increase in heating value
lead to a sulfur dioxide emission reduction of over 40 percent, from
about 0.9 pounds SO2/million Btu (0.4 g SO2/MJ) to about 0.5
pounds SO2/million Btu (0.2 g SO2/MJ).

[0021] Referring again to the effluent 18 from the coal drying process,
the effluent is directed to a cyclone separator 46 to remove coal fines
and other particulate matter, and then the effluent 18 is directed to an
optional flue gas treatment system 48 to remove additional undesirable
components. The gaseous discharge from the flue gas treatment system 48
is vented to the atmosphere. The resulting particulate matter, primarily
coal fines, exiting the cyclone separator 46 is indicated at 50. The coal
fines 50 can be converted into an agglomerated product, as discussed
below.

[0022] The pyrolysis effluent gases 26 leaving the pyrolyzer 22 are first
cleaned in a gas cyclone 52 to remove the coal fines or dust that have
been carried away with the pyrolysis effluent gases 26 from the pyrolysis
process. The pyrolysis gas 54 exiting from the cyclone 52 is then
directed to a knockout drum 56 where heavier tars and coal liquids are
removed from the pyrolysis gas. The pyrolysis conditions in the pyrolyzer
22 are controlled carefully but the existence of small quantities of
these heavier hydrocarbons is unavoidable. The stream of heavier tars and
coal liquids flowing from the knockout drum is indicated at 58. The
knockout drum 56 is capable of dividing the pyrolysis gas 54 into two
streams: the liquid oils and tars 58 and the gaseous lean fuel 60. No
cooling step is required, although a cooling step can be used if desired.
The gaseous lean fuel 60 exiting the knockout drum 56 has a temperature
within the range of from about 550° F. (288° C.) to about
650° F. (343° C.), and is typically about 600° F.
(316° C.). In other embodiments the temperature can be higher or
lower. The lean fuel 60 contains combustible components such as CH4
and CO and since the lean fuel 60 is made in a process that does not
focus predominantly on the production of oils and tars, the lean fuel 60
will be much hotter (600° F. (316° C.) versus about
130° F. (54° C.)) and may be richer than would result from
a process focused more on making oils and tars.

[0023] The resulting lean fuel 60 from the knockout drum 52 can be
supplied to at least three different locations in the apparatus 10 for
treating the low calorific coal. A portion of the lean fuel 60 is
directed to the pyrolyzer combustor 28 to be combusted for the energy
requirements of the pyrolysis step. A portion of the lean fuel 60 is
directed to the dryer combustor 64 to be combusted to supply energy for
the drying step of the process. Finally, a control portion of the lean
fuel is recycled and directed along gas stream 66 to be blended into the
hot pyrolysis gases 24 to control the temperature of the pyrolysis
reaction.

[0024] The dryer combustor 64 is carefully controlled to oxidize the
majority of combustible compounds in the lean fuel 60 at very close to
stoichiometric conditions. Therefore the combustion is run with a
slightly excess oxygen mixture. Too much oxygen could cause reduction of
the quality of the coal in the coal dryer 12. The air or oxygen provided
into the dryer combustor 64 may be preheated, and an auxiliary fuel may
be supplied at 68 to insure that the combustion process will go forward.
Hydrogen, carbon and sulfur are some of the elements that are oxidized.

[0025] The dryer combustor 64 is operated at a temperature above about
1400° F. (760° C.), and typically above about 1450°
F. (788° C.). The combustion gases 70 exiting the dryer combustor
64 are therefore significantly hotter than is desirable for the coal
dryer 14. To control the temperature of the coal drying gas 16 to be
sufficiently cool to substantially prevent volatilization of the
volatiles of the coal in the dryer 14, typically no greater than about
500° F. (260° C.), the combustion gases are mixed with an
auxiliary stream 72 of cooler gases recycled from the cyclone 46, as
shown in FIG. 1. The auxiliary steam 72 is at a temperature below about
300° F. (149° C.), and typically is about 200° F.
(93° C.).

[0026] One of the uses of the lean fuel 60 is that it is supplied to the
pyrolyzer combustor 28 for combustion with additional air. From time to
time auxiliary fuel 62 may also be required, especially at startup. The
temperature in the pyrolyzer combustor 28 must be above about
1400° F. (760° C.), and typically above 1450° F.
(788° C.). The resulting gases 74 exiting the pyrolyzer combustor
28 are too hot for direct introduction into the pyrolyzer 22. Therefore,
a portion of the lean fuel 60 is directed as stream 66 to be mixed with
the pyrolyzer combustion gases 74 to produce the desired pyrolyzer gases
24. Since the process in the pyrolyzer 22 is a mild process, the incoming
pyrolyzer gases 24 should be a temperature less than about 1100°
F. (593° C.), and typically within the range of from about
700° F. (371° C.) to about 900° F. (482° C.).
In some embodiments the incoming pyrolyzer gases could be higher than
1100° F.

[0027] The stream 50 of partially dried coal fines captured in the dryer
cyclone 46, and the stream of coal fines 76 captured in the pyrolyzer gas
cyclone 52 are mixed with the oils and coal tars 58 from the knockout
drum 56. This mixture is then agglomerated in the agglomerator 78 into
briquettes or other agglomerated form, indicated at 80. The agglomerated
particles or briquettes 80 can be sold as a separate high heating value
product, or added to the stream 44 of finished coal char. In one
embodiment, approximately 5 percent of the raw feed coal by weight ends
up as fines that are treated in the agglomerator 78. Other agglomerating
material besides the oils and coal tars 58, or in addition to the oils
and coal tars 58 can be used.

[0028] Important parameters of coal that will be suitable for use in the
process described above include the type of coal, the total moisture in
the raw incoming coal, the ratio of volatile matter to fixed carbon (Fuel
Ratio), and the atomic hydrogen to carbon ratio. The type of coal most
suitable is a non-caking coal, one that typically is a subbituminous
coal, lignite coal, or brown coal. Some of the important parameters of
the coal that will be suitable for use include a moisture content greater
than about 15 percent, a fuel ratio less than about 0.60, and an atomic
hydrogen to carbon (H/C) ratio less than about 0.7. In one embodiment the
raw incoming coal has a moisture content greater than about 20 percent, a
fuel ratio less than about 0.55, and an atomic hydrogen to carbon (H/C)
ratio less than 0.6. The percent moisture, volatile matter, and fixed
carbon in the coal are determined by ASTM D 3172 Standard Practice for
Proximate Analysis of Coal and Coke. The atomic H/C ratio in the coal is
determined by ASTM D 3176 Standard is Practice for Ultimate Analysis of
Coal and Coke.

[0029] The percent moisture, volatile matter, and fixed carbon in the coal
are determined by ASTM D 3172 Standard Practice for Proximate Analysis of
Coal and Coke. In this method the moisture content is defined as the
weight loss when a sample of the as-received material is heated to
105° C. for one hour; the volatile matter is defined as the weight
loss when the dry sample is heated to 950° C. for one hour. The
ash is the material remaining after a sample is burned is the presence of
air. And fixed carbon is determined by difference so that the sum of
percent moisture plus volatile matter plus ash plus fixed carbon equals
100 percent. The atomic H/C ratio in the coal is determined by ASTM D
3176 Standard Practice for Ultimate Analysis of Coal and Coke. In this
method the percent carbon, hydrogen, nitrogen, and sulfur are determined
by combustion analysis. Oxygen is determined by difference so that the
percent moisture plus ash (from the proximate analysis) plus percent
carbon, hydrogen, nitrogen, sulfur, and oxygen equals 100 percent.

Example I

[0030] Two coal samples having relatively low fuel ratios (low percentages
of volatile matter relative to the fixed carbon) were studied. The
characteristics of the coal samples as determined by the ASTM proximate
and ultimate analyses are given in Table I. The coal samples were then
subjected to a laboratory scale processor to determine oil yield. The
results of the analysis are shown in Table II. Oil yield (AR) refers to
as to received, and oil yield (DB) refers to dry basis.

[0031] For comparison with the coal samples analyzed in Table I,
additional coal samples that do not fit the criteria listed above, but
rather have higher fuel ratios, were analyzed using the same criteria.
The coal characteristics are shown in Table III, and the results of the
liquid analysis are shown in Table IV.

[0032] It can be seen that the available oil content is much higher in the
samples set out in Table III when compared with the amount of oil
available for samples A and B. Therefore, the value in removing oil from
the coal for samples A and B is low. Accordingly, there is no need for
expensive equipment for extracting significant amounts of oil from the
coal where the coal is of the type known to have a low oil content.

[0033] In one embodiment, the separation process to separate lean fuel
gases from liquids and tars results in removal of only a small portion of
the pyrolysis effluent gases, less than about 20 percent of the pyrolysis
effluent gases as the liquids and tars, with the remainder being the lean
fuel gases. In another embodiment, less than about 10 percent of the
pyrolysis effluent gases are removed as the liquids and tars. In a
specific embodiment, less than about 5 percent of the pyrolysis effluent
gases are removed as the liquids and tars, with the remainder being the
lean fuel gases.

[0034] In another embodiment, the separation process to separate lean fuel
gases from liquids and tars is carried out while maintaining the
pyrolysis effluent gases at a temperature above the condensation
temperature of the pyrolysis effluent gases. Typically the separation
process is carried out at a temperature within the range of from about
600° F. to about 800° F. (about 315 to about 430°
C.). In one embodiment, the separation process is carried out at a
temperature within the range of from about 600° F. to about
700° F. (about 315 to about 370° C.). In yet another
embodiment, the separation process is carried out without substantial
cooling of the pyrolysis effluent gases.

[0035] The principle and mode of operation of this invention have been
described in its preferred embodiments. However, it should be noted that
this invention may be practiced otherwise than as specifically
illustrated and described without departing from its scope.